1. Field of the Invention
The present invention relates to a bending operation apparatus for a tubular insertion member, which is designed to bend the insertion portion of, e.g., an endoscope, or a tubular insertion member such as a catheter in arbitrary directions.
2. Description of the Related Art
In a conventional bending operation apparatus, a bending portion, which can be bent/deformed, is formed at the insertion portion of, e.g., an endoscope or at the distal end side of a flexible tube such as a catheter. The apparatus allows an operator to remotely control a bending operation of the bending portion through an operating portion at hand.
A bending operation apparatus of this type has been developed, which is designed such that small actuators constituted by shape memory alloy (SMA) members, pneumatic type artificial rubber muscles, and the like are arranged at the insertion portion of an endoscope, i.e., the distal end side of a flexible tube, and a bending operation of the bending portion is performed by the small actuators through angle wires.
In this case, a plurality of bending pieces are arranged in the bending portion along its axial direction and are pivotally coupled to each other. One end of each angle wire is fixed to the distal end of the bending portion. Each of the above-mentioned small actuators is fixed to the other end of a corresponding one of the angle wires.
When the small actuators are operated, two or four angle wires are pulled, thus freely bending the bending portion in two or four directions through the respective bending pieces.
If the apparatus is designed such that four angle wires are independently pulled to allow bending operations in four directions, the bending portion of the endoscope can be aimed in an arbitrary direction within a range of 360.times. by combining bending operations performed through a plurality of angle wires.
In the conventional bending operation apparatus having the above-described arrangement, however, small actuators, equal in number to the bending directions of the bending portion, must be independently arranged at the distal end side of the flexible tube. For example, if four angle wires are used to bend the bending portion in four directions, four small actuators need to be independently arranged at the distal end side of the flexible tube. This interferes with a reduction in the diameter of the flexible tube.